Optical networks, such as OTN (Optical transmission network), WDM (Wavelength-division multiplexing), SDH (Synchronous digital hierarchy) or SONET (Synchronous optical network) have been widely applied in the telecommunication field.
Recently, the automatic switched optical network (ASON) is one of research hotspots in the field of optical networks. The concept of ASON is offered by ITU-T G.8080, and the function of ASON is achieved through a specific Control Plane (CP). ITU-T G.7713 specifies the framework to implement distributed calls and connections in ASON and offers the implementation criterion for automatically establishing, modifying and deleting the calls and connections. Standards such as ITU-T G.7715 offer the implementation model and method for the route inquiry of connection (the route inquiry described in the following refers to the route inquiry of connections, unless especially declared).
However, the published ITU-T G.7715 and ITU-T G.7715.1 apply the model shown in FIG. 1. In this route model, when a certain network element (NE) in ASON needs to query the route of connection, the Connection Controller (CC) which is responsible for the connection control (including establishment, deletion, modification, and so on) sends the Route Request to the Route Controller (RC) which is responsible for route inquiry and calculation, and then the RC calls a route algorithm (a typical route algorithm is Constrained Shortest Path First, shortly CSPF) according to the Route Request and calculates the route based on the routing database (RDB) of the node and returns the route calculation result (Route Response for short) to the CC.
However, the RDB of a node is generally hard to have the complete route information of the whole ASON, thus the model shown in FIG. 1 can not meet the requirements of route inquiry and calculation. Therefore, the model shown in FIG. 2 is offered in the related technology in recent years, and the model is derived from the model shown in FIG. 1, that is, when the CC of a certain NE in the ASON launches a Route Request of a connection to the RC, the RC will call CSPF according to the Request and implement the route calculation based on the RDB of the node. If the related route can not be found, the local RC will transmit the Route Request to another related ASON NE having a more complete RDB through protocol control component (PC for short). The RC of the other related NE calls CSPF after it receives the Route Request through PC and completes the route calculation based on the RDB of the node, and returns the Route Response to the ASON NE which launches the Request. This ASON NE will return the Route Response to its CC.
ITU-T G.8080 suggests that the CP in ASON should apply a flexible framework, that is, any ASON NE may lack a certain component, e.g., RC. Therefore, if a ASON NE without RC which needs to query the route, the route inquiry can not be implemented by either the method shown in FIG. 1 or the one shown in FIG. 2.